Cl_chart_engine is not refreshing with new value.

HI All ,

            I am passing the value of internal table for the first time it is updating the correct graph , but after pressing the back button i am passing new value to the internal table and but  graph is not refreshing .

             LOOP AT gt_chart INTO gwa_chart.

             lobj_element = xu_ixml_doc->create_simple_element(

             name = 'C' parent = lobj_categories ).

            lobj_element->if_ixml_node~set_value( gwa_chart-text ).

            lobj_element = xu_ixml_doc->create_simple_element(

           name = 'S' parent = lobj_series ).

           lobj_element->if_ixml_node~set_value( gwa_chart-value ).

           endloop.

Reagards

Kishore